TOTAL ECLIPSE OF THE SUN, JANUARY 22, 1898. 
193 
In each case, some of the spare light from the mirror was utilized for a small 
telescope adjusted to act as a finder to the prismatic camera. The one used with 
the 9-inch instrument was arranged to view the image directly with an eye-piece, 
hut that employed with the 6-inch was arranged to give an enlarged image on a 
white screen. 
Each instrument was provided wuth plateholders similar to those employed in 
Brazil in 1893.* Four slides were used with the 6-inch, two holding plates 
12" X 10", and two holding four plates each 12" X 2". For the 9-inch two of the 
plateholders carried plates 16" X 6|", and three carried three plates each 6|-" X 2". 
The instruments were focussed hy taking trial photographs of stellar spectra. 
Mr. Fowler and Dr. Lockyer, who were in charge of the 6-inch and 9-inch 
respectively, were each assisted by a number of volunteers from H.M.S. “Melpomene,” 
who were distributed as follows :— 
Ill charge of finder and 
chronometer . . . . 
In charge of siderostat and 
to make exposures . 
Recorder of exposimes . 
To hand and receive dark 
slides. 
In charge of lamp . 
6-inch. 
Lieutenant Df: Wet, R.N, 
Turner, 1.1. 
C. Ironsides, G.M. 
T. Brading, A.B. 
J. Innes, A.B. 
E. Salt, Boy, 1st Class. 
9-inch. 
Lieutenant Percival Jones, R.N.R. 
W. Bray, Ch. Arm. 
A. Ramage, A.B., L.T.O 
A. Wilkins, Shipwright. 
E. Ashford, A.B. 
F. Fenton, A.B. 
A. Carr, Boy, 1st Class. 
The duty of the observer in charge of the finder was to keej^ the image in the 
centre of the field of view, which corresponded by previous adjustment with the 
centre of the })late in the prismatic camera ; records of the moments of contact 
were also made. 
The exposures were made by means of a piece of cardboard which was used to 
cover or uncover the front of the prism from directions given by Mr. Fowler and 
Dr. Lockyer respectively. 
In the two prismatic cameras fifty-seven photographs were secured, the exposures 
varying from 1 to 50 seconds. Such a result as this could only be obtained by a 
minute subdivision of labour. 
Local Conditions of Eclipse as affecting the Prismatic Cameras. 
The small difference in the ajDparent diameters of the sun and moon (see 
Part L, p. 156) was a very favourable circumstance in connection with the work 
of the prismatic cameras relating to the chromospheric spectiaim, for the reason that 
the arcs of chromosphere visible at the beginning and end of totality woulcl be 
VOL, CXCVJI.-A. 
* ‘ Phil. Trans.,’ A, vol. 187 (1896), p. 571, 
2 c 
